This invention relates to rotating machines, e.g. rotary compressors and scroll compressors for refrigeration or air conditioning, especially compressors of the type which are hermetically sealed and have a vertical rotating shaft that serves as both a rotor shaft and as a centrifugal lubrication pump. The invention is more particularly directed to a rotor assembly construction which provides a greater lubricating capacity and also increases the efficiency of the compressor.
In rotary compressors and scroll compressors, an electric motor drive is built into the housing or shell, and has a stator or electric armature affixed in the shell and a rotor assembly that fits into a cylindrical passage in the stator. The rotor assembly has a shaft that is rotationally supported and journalled in a bearing housing, in some cases at one side of the rotor and in some cases both above and below the rotor. As these compressors are situated vertically, i.e., with the rotor axis vertical, lubricant reposes in a sump or reservoir at the lower end of the shaft. Typically, the rotary motion of the rotor shaft is availed upon as a single-stage centrifugal pump to drive the lubricating oil upward by centrifugation. That is, an oil tube at the lower end of the shafts dips into the reservoir and picks up the oil, which moves upward into a hollow center of the shaft. The conventional shaft has one or more axial bores disposed off axis to carry the oil to the top of the shaft, where the oil proceeds through one or more lubricating channels to oil the bearing or bearings and other moving parts. A central axial bore in the shaft serves as a vent.
The requirement for the several bores, which must be positioned in the shaft, raises the production cost of the rotor assembly. Also, the shaft has to be of a rather large diameter to accommodate the lubrication bores or channels. This necessitates a larger center bore in the laminations that make up the rotor, with a consequent reduction in magnetic material towards the axis. There are significant eddy current losses involved, which it would be desirable to reduce.